Patent Document 1 discloses a method to determine the degree of degradation of a fat by oxidation by mixing and agitating the fat being tested with a reagent, and measuring the degree of coloration caused by the reaction between the fat oxide in the fat being tested and the reagent.
Also, Patent Document 2 discloses a fat degradation measuring device that determines the degree of degradation of fat by irradiating light onto a coloring unit in which different colors are produced in accordance with the degree of degradation of the fat that has reacted, receiving the light reflected by the coloring unit, determining the degree of degradation of the fat based on information on the strength of the reflected light and comparative information, and displaying the degree of degradation.